BACKGROUND: The aim of the present study was to investigate the stability and longitudinal association between depression and smoking status within a community sample with type 2 diabetes (T2D) while controlling for sociodemographic and disease-related variables.

METHODS: Adults with T2D were recruited and agreed to be followed-up via random digit dialing for the Montreal Diabetes Health Study. At baseline, 1614 individuals were classified as never (n = 592), former (n = 690), light (≤10 cigarettes a day; n = 128) and moderate-heavy (11+ cigarettes a day; n = 204) smokers. Depression was assessed using the Patient Health Questionnaire-9 and individuals were classified as either "none" or having depression syndrome. Generalized estimating equations were used to test the association between depression syndrome and current smoking status while controlling for other demographic and health-related variables.

CONCLUSIONS: Smoking and depression prevalence rates appear to be stable over time in our community sample with T2D. Moderate-heavy smoking is strongly associated with elevated depression, both in cross-sectional and longitudinal models. Persistent moderate-heavy smokers may be at increased risk of both physical and mental health complications. This burden is even greater for those with T2D.

OBJECTIVE To evaluate the association between recurrent subthreshold depressive episodes and functioning in a prospective community sample of people with type 2 diabetes. RESEARCH DESIGN AND METHODS A prospective community study in Quebec, Canada, was carried out between 2008 and 2013 (n = 1,064). Five yearly follow-up assessments (telephone interviews) were conducted. Baseline and the first three follow-up assessments were used to identify recurrent subthreshold depressive episodes (Patient Health Questionnaire [PHQ]-9). Functioning (World Health Organization Disability Assessment Schedule II [WHODAS-II]) and health-related quality of life (Centers for Disease Control and Prevention [CDC] unhealthy days) at 4- and 5-year follow-up assessments were the outcome measures. RESULTS Nearly half of the participants suffered from at least one episode of subthreshold depressive symptoms. After adjusting for potentially confounding factors, the risk of poor functioning/impaired health-related quality of life was nearly three times higher (relative risk = 2.86) for participants with four subthreshold depressive episodes compared with participants with no/minimal depression. Results suggest a dose-response relationship: the risk of poor functioning/impaired health-related quality of life increased with the number of recurrent subthreshold depressive episodes even after controlling for potentially confounding variables (significant linear trend, P < 0.001). CONCLUSIONS Recurrent subthreshold depressive symptoms might be an important risk factor for poor health outcomes in type 2 diabetes. Early identification, monitoring, and treatment of recurrent subthreshold depressive symptoms might improve functioning and quality of life in people with type 2 diabetes.